For example, as this type of vibration isolation device, a configuration described in the following Patent Document 1 is known. This vibration isolation device includes a tubular first attachment member which is coupled to one of a vibration generating part and a vibration receiving part, and a second attachment member which is coupled to the other thereof; an elastic body which couples both the attachment members together; and a partition member which partitions a liquid chamber within the first attachment member having a liquid enclosed therein into a first liquid chamber and a second liquid chamber. This vibration isolation device further includes a first limit passage and a second limit passage which allows both the liquid chambers to communicate with each other, a cylinder chamber which is provided between both the liquid chambers, and a plunger member disposed so as to be movable between an open position and a blocking position within the cylinder chamber.
For example, vibrations of a plurality of kinds having frequencies different from each other, such as idle vibrations and shake vibrations, are input to this vibration isolation device. Thus, in this vibration isolation device, the respective resonant frequencies of the first limit passage and the second limit passage are set (tuned) to the respective frequencies of the different kinds of vibration. As the plunger member moves between the open position and the blocking position according to the frequencies of input vibrations, a limit passage through which a liquid flows is switched between the first limit passage and the second limit passage.